India's powerful lower house of parliament has passed a landmark anti-corruption bill that seeks to create an independent ombudsman with powers to investigate corruption charges against bureaucrats and politicians.

The bill was passed Tuesday following hours of heated debate in parliament and a staunch defense from Prime Minister Manmohan Singh.

Anti-corruption activist Anna Hazare launched a three-day hunger strike in Mumbai to coincide with the parliamentary debate. He called on the government to redraft what he called the "toothless" legislation, saying the proposed ombudsman will be controlled by the government, making it ineffective in tackling rampant corruption.

The 74-year-old activist also threatened a wider civil disobedience campaign starting Friday in which activists will voluntarily go to jail if their demands are not met.

Opposition leader Sushma Swaraj of the Bharatiya Janata Party denounced the Lokpal Bill as flawed. But the government says the proposed law is a fine piece of legislation and will be instrumental in fighting corruption.

The Congress Party-led government failed to get the two-thirds' majority it needed in the lower house to make the bill a constitutional amendment. The legislation now must gain approval in the upper house and be signed by the president before it goes into effect.

The government hopes to pass the landmark legislation by Thursday. But its fate is uncertain, with opposition parties expected to seek many changes.

Public frustration over a series of multi-billion-dollar corruption scandals involving top politicians has been growing.

Hazare, who claims inspiration from Mohandas Gandhi, held a similar 12-day fast in August to protest an earlier draft of the legislation. That strike stoked public anger against what is seen as widespread corruption in Indian society, and brought millions of Indians onto the streets nationwide.

Rishi, an organizer of the latest fast, says his group is preparing for tens of thousands of protesters to show solidarity with Hazare in Mumbai. "The preparations started two days ago. The carpeting area in the front can accommodate 15,000 people who will come here to support it," he said.

Hazare's critics say his methods go outside the bounds of India's democratic system, adding that he is forcing his political views on parliament.

"It is the job of the parliament to make the legislation. We had several rounds of discussions with Shri Anna Hazare and his team," said Indian Finance Minister Pranab Mukherjee. "We know their viewpoints, but it is for the parliament to decide what would be the final shape of the legislation."